1. 安装JDBC

1. 官网地址：官网地址
2. 选择
   
3. 下载后，解压缩，然后将mysql-connector-j-9.0.0.jar文件放到项目目录下

编写操作数据库代码

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class HelloWorld {
    public static void main(String[] args) {
        Connection conn = null;
        Statement state = null;
        ResultSet ret = null;

        try {
            // 加载JDBC驱动程序
            Class.forName("com.mysql.cj.jdbc.Driver");
            // 建立数据库连接
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/dbname", "username", "password");
            // 创建statement对象
            state = conn.createStatement();
            // 执行查询
            String query = "select * from tablename";
            ret = state.executeQuery(query);
            // 处理结果
            while (ret.next()) {
                String columnValue = ret.getString("columnname");
                System.out.println(columnValue);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (ret != null) ret.close();
                if (state != null) state.close();
                if (conn != null) conn.close();   
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

编译运行

javac -encoding utf-8 .\HelloWorld.java
java -cp ".;mysql-connector-j-9.0.0.jar" HelloWorld